We will investigate our newly developed inhibitory dual receptor hypothesis regarding the properties of autoantibodies to apoptotic cell membrane (ACM) determinants, which selectively discriminate cells dying from apoptotic death from healthy cells. We have discovered that anti-ACM antibodies form immune complexes with apoptotic cells that trigger anti-inflammatory signal transduction pathways. Therefore, our studies will characterize the mechanistic features by which ACM antibodies are postulated to enhance interactions with dual sets of inhibitory receptor; for early complement factors and for apoptotic cells. In particular, our investigations point to a critical interaction with the TAM family of receptor tyrosine kinases. To understand the greater relevance to pathogenesis, we will also investigate whether and how anti-ACM antibodies block the pro-inflammatory effects of pathogenic IgG autoantibodies to nuclear antigens, postulated to trigger TLR7 and TLR9. We will be characterize and visualize the in vitro inhibitory effects for IgG-nuclear antigen complexes, and we will also study their immune modulatory properties on the in vivo disease activity in murine models of autoimmune glomerulonephritis. Moreover, to investigate the relevance to clinical disease, we will also assess whether there is a correlation between levels in SLE patients of IgM and IgG subclass-specific anti-ACM autoantibodies and with lupus- associated autoantibodies, and with protection from certain features of lupus clinical disease activity. We anticipate that these studies will reveal new insights into immune regulation and autoimmune pathogenesis, and provide the essential bridge from basic studies to the development of a new therapeutic approach to the treatment of SLE.